Antenna Gain - Is it the ultimate measure of a better antenna?

[FOX TV]

Agreed.

What I'd like to see is a re-release of that old, legendary to the point of being almost mythical Radio Shack 15-624 2-bay antenna.

Oak Entertainment Centers and Home Office Furniture, TV Antennas, Audio/Video, Satellite, Cable, DSS was selling them via Antenna Craft up till about a year ago but the RS 15-624 is no longer available from there or anywhere else that I'm aware of.

I own one of those and that dude picks up WWHO from 54 miles away without any drop-outs what so ever.

What I'd really like to see is for some enterprising company to take the same design and turn it into a 4-bay or better yet an 8-bay antenna. Heck, with an 8-bay version of the RS 15-624 I could be sitting here in Ohio watching the Fishing Network out of Puget Sound, Wa.

OK, that last bit was a big exaggeration (mythical) and only for laughs but that is a great UHF antenna and the potential of a 4 or 8-bay version of it would be interesting to say the least. And the RS 15-624 is right around 20% smaller than other 2-bays.

Here's a pic of the one I have planted in my attic.

What are the dimensions of the butterfly elements, the distance between the elements top to bottom, and the side to side distance between the butterfly elements? This would be an easy antenna for me to fabricate if I had all of the dimensions off of an original antenna.

The first thing I see is that the back plane could be made from an old refrigerator or oven rack, or if you can weld, it can be made from round stock or brazing rods and welded together and sprayed with cold galvanizing spray to keep it from rusting, and lexan pieces can be used for the insulators.

It looks like I already have all of the stuff I would need to make one in my garage, if only I had the dimensions... I even have an old stove in my basement I could steal a rack out of to use for the back plane if the spacing is close, but I normally prefer a screen reflector back plane over an open grid or rods.

Even though the picture gives a lot of detail, the measurements could be helpful for anyone who wants to fabricate a copy of this antenna, since it is no longer in production, and I assume the patents ran out a long time ago if it was sold in the 1960's. I would like to build one of these and see if the "LEGEND" is true.

 

[Don_M]

What are the dimensions of the butterfly elements, the distance between the elements top to bottom, and the side to side distance between the butterfly elements? ...

Even though the picture gives a lot of detail, the measurements could be helpful for anyone who wants to fabricate a copy of this antenna, since it is no longer in production, and I assume the patents ran out a long time ago if it was sold in the 1960's. I would like to build one of these and see if the "LEGEND" is true.

You might be interested in Ken Nist's take on this antenna. He lists some, but not all, of its dimensions.

Radio Shack called this antenna the "Golden U" and sold it from when I worked there in the mid-70s until it was discontinued circa 1990. It was probably our biggest-selling antenna since it was so cheap and worked so well. No wonder: Most of Boston's UHF broadcasts at the time were above channel 35, where this design is strongest.

 

[Tim58hsv]

Some of these measurements are approximate due to wear an tear and may be off by an 1/8" give or take.

RS 15-624 dimensions

Reflector screen: 12.5" X 12.5"
Spacing between reflector and dipoles: 2"

Bowtie dimensions
Length: 5 3/4"
Width: (flat bowtie) 1" to 5 1/4"
Width: (folded bowtie) 1" to 3 7/8" (outer tip to outer tip of each bowtie). The center of each bowtie is 1" wide.

Horizontal space between bowties is 1"
Vertical space between bowties is 4 1/2" for the outer edge of bowties and 8 1/4 from center of upper bowtie rivet to the lower bowtie rivets center.

Phasing bars are 9" long with 1 3/4" in between bars.

Good Luck and let us know how it goes.

 

[Tim58hsv]

You might be interested in Ken Nist's take on this antenna. He lists some, but not all, of its dimensions.

Radio Shack called this antenna the "Golden U" and sold it from when I worked there in the mid-70s until it was discontinued circa 1990. It was probably our biggest-selling antenna since it was so cheap and worked so well. No wonder: Most of Boston's UHF broadcasts at the time were above channel 35, where this design is strongest.

Thanks for the link, Don.

Ken says it was a Channel Master antenna and not a Antennacraft model which was what I mistakenly thought. Ken also calls it a 15-623. I understand that was it's original ID but was later known as the 15-624. Maybe the difference was (which EscapeVelocity spoke of earlier here) that the 15-623 was the sturdier model and the 15-624 was it's more flimsy cousin. Not sure which one I have but it did come from Radio Shack and seems pretty sturdy.

I've often heard that it's not great on the lower uhf channels and that sounds right. It's great for picking up channel 53 (WWHO rf 46) at 54 miles away but does have trouble with channel 19 (WXIX rf 29) at 42 miles away.

 

[EscapeVelocity]

This as regards the Corner Reflector and Plane Reflector Bowtie antennas from MJ Salvati's TV Antennas and Signal Distribution Systems...page 182.

...The deciding factor for front-to-back ratio of uhf antennas is essentially the quality of the reflector. For example the antennas witht he best front-to-back ratios in Ch. 3 were those having wire-mesh or steel grille plane reflectors, or corner reflectors with apex and closely space rods. Corner reflector antennas and corner reflecting yagis missing an apex rod (typical of there type) have sizable backlobesat the highend of the band where the refelctor is no longer sufficiently opaque. Finally, the very-high gain AntennaCraft Hoverman G1483 array has the worst front-to-back ration of the recommended antennas because ti has just a few widely spaced half-wave elements to act as a reflector for the large area of the driven element. While an antenna of this type is excellent for fringe areas (where ghosts rarely are a problem), it is a poor choice for a metropolitan area (where ghosts usually are a problem). The best ghost fighting antennas for uhf frequencies are of the 4 bay bowties or the Corner Reflectors with apex rod reflectors. Both of these style antennas also have good vertical-plane discrimination, so they are better than most others for rejecting ground and aircraft reflections.

Also note that the corner reflector UHF yagis, tighten the beamwidth at the upper frequencies around the resonant frequency of the directors....then gain drops off severely above that resonant director frequency. So the horizontal beamwidth tightens significantly on the upper UHF channels....from say around 45 degrees for a 4 bay to around 30 degrees for a Corner Reflector Yagi. On the lower end of UHF both the 4 bay bowtie and the Corner Reflector Yagi are around 60ish degrees beamwidth.

Hope that makes sense.

 

[EscapeVelocity]

Gavin CR-5 aka Radio Shack 15-1629

From MJ Salvati's TV Antennas and Signal Distribution Systems...

Another good corner reflector with useful and unusual characteristics is the Gavin CR-5. This antenna provides 7-10 dBd gain over the entire UHF band from channel 14 to 83, a respectable performance considering its rather small size. Unlike most other antennas, the gain of the CR-5 does not fall off after Channel 70k, but remains near the 10 dB mark. The beamwidth is very consistent across the entire UHF frequency spectrum, something unusal for corner reflectors. This antenna is the lowest priced of the corner reflectors.

Note, mine has a apex reflector rod directly behind the bowtie, which is different from the pic in Salvatis book. This is good, as it improves F/B ratio at higher UHF frequencies and slightly increases gain.

 

[tballister]

Hey Piggie:

I finally took a moment to visit this thread. As I mentioned somewhere else, I'm in the middle of authoring another page under my Antenna Hacks website called "Quantity vs Quality" (really original, huh?).

I think the focus is exactly on the question you've posed in this thread, and I understand why you've become so sensitive to the question, and I empathize with you. I have similar issues, and it sounds like FoxTV does as well. I live in the Sierra Mountains about 30 (Interstate 80) miles west of Reno, NV. LOS to the VHF and some of the UHF towers is about 11 miles, and LOS to the local Fox affiliate is 18 miles and 75 degrees north of the others.

I'm at about 5900 feet, the main VHF/UHF are at about 9500, and in between is a perpendicular ridge at just over 10,000 feet. A perfect Knife Edge to experiment with!

I'm also a member of the local SBE (Society of Broadcast Engineers), and all my friends there know that I spend way too many hours staring at the Spectrum Analyzer to be of sound mind.

Nevertheless, my observations have led to a modest perception (at least) of what's good, and what' not so good. What I think we both understand is that you can have two signals, 1 with significantly higher field strength than the other, like 10 dB for example, and yet the weaker signal will be dramatically higher on your DTV "Quality" indicator.

When viewed on the analyzer the reasons become clear quickly. If the stronger signal's envelope is full of serrations, or significantly dipped/peaked across its ~6MHz bandwidth, while the weaker signal is flat as a pancake, it explains everything. And if you had such an analyzer, I wager you'd spend just as much time staring at it as I do! :hungry:

Anyway, after reading your initial post to this thread I got to thinking (dangerous). In my tool kit I also have a DIGIAIR PRO; its a cute little RF Level meter that you can take up the ladder with you (much cheaper and lighter than the Specturm Analyzer). I was just wondering what you might be able to do if you had just such a little RF meter. I was wondering if you might be able to at least infer (not conclude) what the quality is of your available signals, on a bit of a relative basis.

I was thinking that if you did a little spreadsheet of received level of each station, versus your DTV receiver's indicated digital "quality" number, then do an x-y "scatter" plot, you might see something interesting. It would be crude, I know, but if "quality" (again, as indicated by the somewhat arbitrary manufacturer-to-manufacturer internal algorithms in DTV sets) were proportional only to level, then most points would lie generally along some trend line or curve, maybe linear near the low end and probably asymptotic near the high end.

Those points that deviate from the curve, or general trend line, are the points under the influence of something (hic) other than just signal level.

Dunno, for sure, just thought it might be interesting. Maybe I'll do it myself, but I only have 7 data points here.

Anyway, I really do empathize with your struggles. I'm happy to have found this forum where related notes and experiences can be compared. Thanks for starting it!

Best Wishes,
t

 

[tballister]

Haunting Words

The most recent posts here discussing the merits of models like the Radio Shack 15-624 and Gavin CR-5, which employ solid metal dipoles as opposed to wire outlines, make me recall the following words from the "Antenna Engineering Handbook, 2nd Edition, Johnson & Jarek". I hope I'm not violating a copyright by posting the following paraphrase.
-------------------------------Quote-------------------------------------
A dipole formed from two triangular sheets of metal is sufficiently broadband with respect to gain and VSWR (with respect to 300 Ohms) for all-UHF-channel reception. ... The Triangular dipole has many of the same pattern and input-impedance characteristics of the biconical dipole, but is lighter in weight and simpler to construct. Further simplification of the triangular dipole to a wire outline of the two triangles results in significant degradation of its broadband performance. However, the metal triangles can be approximated with wire mesh, provided the mesh spacing is less than one-tenth wavelength.
-----------------------------End Quote-----------------------------------

Its those words about the effect of simplifying to a wire outline that have haunted me for some time.

What if ...

t

 

[EscapeVelocity]

Indeed. Digitenna brought back the sheet metal solid bowtie.

 

[tballister]

Now on a non-LOS stations like Jacksonville is from my house. LOS to them is about 400 ft AGL at my house, yet I am only up 30 ft, mainly to get 4 wavelengths above my metal roof where you get away from most effects of the roof.

Piggie:
I meant to comment on this in my last post, but it was starting to run on..

I also have a metal roof. But I've also found it delightfully advantageous

Its kind of like, "step back from your house, then look at it and list the reception related electro-mechanical components you see". Obviously wire, mast, antenna(s), amplifier, etc. But if you've got a metal roof, you've also got a ready made reflector!

I posted a comment somewhere else about a C5 experiment I'd done. I popped one on a 20' pole quickly just to see what I could see. I was near the edge of my porch and roof so that the roof wasn't really under the LOS.

But then I moved further in towards the roof peak such that a major portion of the roof was under the LOS and noticed a dramatic level increase! I found there was a sweet spot, I think 5' or so above the roof where things were optimal.

I also did the same experiment with a DB8 and a 91XG pointed in a completely different direction. There was also a major sweet spot, in this case about 8' above the roof.

The cool thing is that its largely unaffected by 2' of snow dumped on it; very important where I am!

Just FYI.
t

 

[Piggie]

The most recent posts here discussing the merits of models like the Radio Shack 15-624 and Gavin CR-5, which employ solid metal dipoles as opposed to wire outlines, make me recall the following words from the "Antenna Engineering Handbook, 2nd Edition, Johnson & Jarek". I hope I'm not violating a copyright by posting the following paraphrase.
-------------------------------Quote-------------------------------------
A dipole formed from two triangular sheets of metal is sufficiently broadband with respect to gain and VSWR (with respect to 300 Ohms) for all-UHF-channel reception. ... The Triangular dipole has many of the same pattern and input-impedance characteristics of the biconical dipole, but is lighter in weight and simpler to construct. Further simplification of the triangular dipole to a wire outline of the two triangles results in significant degradation of its broadband performance. However, the metal triangles can be approximated with wire mesh, provided the mesh spacing is less than one-tenth wavelength.
-----------------------------End Quote-----------------------------------

Its those words about the effect of simplifying to a wire outline that have haunted me for some time.

What if ...

t

Thank you a 100 times T! I have been saying this over and over and could not find the where I had read this in my past. So now maybe this carries more weight in the discussions, that 2 wires forming part of the outline are not as good as a solid triangle. I have often though this is why with the Channel Master 4149 Double Bow Tie the user reveiws that just look to which channels they receive are much better than the fact this antenna (I believe but not sure) might go back all the way to having channels 14-83. In other words people that just bought them and put them up had great things to say, whereas those that modeled this antenna constantly point out it not a good low UHF performer.

 

[Piggie]

Piggie:
I meant to comment on this in my last post, but it was starting to run on..

I also have a metal roof. But I've also found it delightfully advantageous

Its kind of like, "step back from your house, then look at it and list the reception related electro-mechanical components you see". Obviously wire, mast, antenna(s), amplifier, etc. But if you've got a metal roof, you've also got a ready made reflector!

I posted a comment somewhere else about a C5 experiment I'd done. I popped one on a 20' pole quickly just to see what I could see. I was near the edge of my porch and roof so that the roof wasn't really under the LOS.

But then I moved further in towards the roof peak such that a major portion of the roof was under the LOS and noticed a dramatic level increase! I found there was a sweet spot, I think 5' or so above the roof where things were optimal.

I also did the same experiment with a DB8 and a 91XG pointed in a completely different direction. There was also a major sweet spot, in this case about 8' above the roof.

The cool thing is that its largely unaffected by 2' of snow dumped on it; very important where I am!

Just FYI.
t

Very interesting and have heard this before. My situation are chs 7, 10, 13 all VHF. Believe me when I say I tried all sorts of distances between the vertically stacked YA-1713s and how high they were. 30 ft things came alive. At 45 ft (limit of my pushup pole, they were slightly better, but not enough to justify guy wires and such. But below 30 ft the signal quality dropped rapidly. The roof is behind it as part of a corner reflector. With the bottom edge of the roof where the pole is mounted about 11 ft and the top of the roof horizontally 12 ft behind the stack and 14 ft above the ground.

I suppose though with the results I had raising it with it coming alive at 30 ft then only slightly better up to 45 ft, it was more getting above something else than the positive effects of the roof. Maybe a ground reflection, maybe negative effects of the roof.

Now if WESH 83 miles from a 500 meter tower and 2 edge and WNBW from a 300 meter tower at 37 miles and LOS both seem to have sweet spots around the yard. The Jacksonville stuff seems to like pure height above the ground anywhere in the yard.

No sure why or what I found except how to pick up Jacksonville (well most of the time).

 

[tballister]

... The roof is behind it ...

In both of my cases, the benefit comes where the roof is forward of and below the antenna. Feels like some kind of advantageous equivalent of a ground reflection...
t

 

[Piggie]

In both of my cases, the benefit comes where the roof is forward of and below the antenna. Feels like some kind of advantageous equivalent of a ground reflection...
t

Well this might work on WESH-24 a translator yet to be build but most likely will be build due to who owns the license. That will be straight over the roof.

As I said my VHF path to Jax, the roof is behind the antenna.

I am wondering. I have never in years of playing with antennas seen any really good hot spots in FL. I wonder if edge refraction on UHF lends to more hot spots.

 

[tballister]

As I said my VHF path to Jax, the roof is behind the antenna.

I am wondering. I have never in years of playing with antennas seen any really good hot spots in FL. I wonder if edge refraction on UHF lends to more hot spots.

Have you ever experimented with the antenna behind the roof?

From what I've read, I'm pretty sure diffraction and frequency are inversely proportional. I.e., for two frequency sources, both collocated, there will be less diffraction for the higher frequency. But we're only talking 1 1/2 octaves diff between VHF and UHF. Hmmm... only my intuition, but for wavelength identical reflective surroundings I'd guess there would be just as many hotspots, but they'd be closer together for the shorter UHF wavelengths, and thus more of them in a given area?

 

[RF Engineer]

The web is full of fake gain and distance claims and since 95% use DB gain over the non existant "isotropic radiator"
their gain numbers can never be proven

Winegard is still the only one that quote DB gain over a DIPOLE which is the only valid reference to us for TV antennas and always will be.